Screen plate



Sept. 11, 1923.

W. S. HALL SCREEN PLATE Filed Sent. 2. 1921 To all whom it may concern Patented Sept. ll, 1923.

entree stares WALTER S. HALL, OF FITCHBUBG, MASSACHUSETTS.

SCREEN PLATE.

Application filed September 12, 1921. Serial No. 499,992.

Be it known that I, VVALTER S. I'IALL, a citizen of the United States, residing at Fitchburg, in the county of Vvorcester and Commonwealth of Massachusetts, have invented a new and useful Improvement in a Screen Plate, of which the following, together with the accompanying drawings,

is a specification.

My invention relates to the manufacture of screen plates, as commonly employed in paper mills, for screening the wet ,pulp

prior to its formation into sheets'of paper.

The object of my invention is to provide an improved method of making screen plates, by the practice of which. screen plates may be produced that are adapted to handle a much larger amount of pulp than the screen plates heretofore employed. These and other advantageous features of my invention will hereinafter more fully appear, reference being had to the accompanying drawings in which,

Fig. 1 is a diagrammatic view'showing the use of a screen plate formed in accordance with myinvention in connection with the screening of paper pulp.

Fig. 2 is a plan view looking at the under side of a portion of the plate shown in Fig. 1. y

Fig. 2 is a plan view. similar to. Fig. 2 showing a portion of a screen plate, as previously constructed.

Fig. 3 is a transverse sectional view of a portion of the plateshown in Fig. 1 showing the first step in the. manufacture of a ,)late in accordance with my invention.

ig. 3 is a transverse sectional view. of a plate showing the first step in the manufacture of a screen plate, as previously constructed.

Fig. l is a view similar to Fig. 3 showing.

the second step in the manufacture of a screen plate in accordance with my intion.

Fig. 4 is a view similar to view in Fig. 3 showing the second step in themanufacture of a screen plate, as previously constructed.

Fig. 5 is a fragmentary View of a portion of a screen plate and illustrating the final steps in the manufacture of a screen plate in accordance with my invention;

Fig. 6 is a fragmentary view similar to Fig. 5 showing a portion of a completed screen plate.

Fig. 7 is a view partially in perspective and partially in transverse section showing a portion of a completed screen plate con structed in accordance with my invention.

Fig. 7 is a view similar to Fig. 7 showing a portion of a completed plate, as previously constructed. i

Fig. 8 is a sectional view along the line 8-8 of Fig. 2.

Like reference characters refer to like parts in the different figures.

Referring to Fig. 1, a screen plate 1 is supported 111 an open vat 2, the bottom of' which is constituted by a flexible diaphragm The diaphragm 3 is connected to a rod 4 that is adapted to be alternately moved up and down by means of a cam 5, mounted on a rotating shaft 6, thereby imparting a vibratory movement to the diaphragm 3.

As bestshown in Figs. 6, 7 and 8, the

top of the plate 1 is provided with a plurality of narrow slots 7, each of which communicates with a slot 8 provided on the under side of the plate 1. The slots 8 are considerably wider than the slots 7 and eX- tend almost through the plate 1, leaving thin shoulders 9 on opposite sides of each slot 7. In using plate 1 in a paper mill, the pulp, miXed with a large amount of water, is allowed to flow on to the top of plate 1 andwhen the diaphragm 3 is vibrated by the rotation of the shaft 6, the pulp fibres are sucked through the slots 7 down on to the diaphragm 3 from which the pulp is removed by any suitable means, not/shown. I In passing through the slots 7, the pulp fibres are all turned parallel to the length of the slots and it is of the utmost importance that in passing'through the slots 7, the fibres do not catch on any projections which might tend to form them into strings hanging downwardly from the plate 1.

Referring to Fig. 3, the first step in the manufacture of a plate in accordance with my invention consists in forming the slots 8 by means of an ordinary rotary cutter 10.

turned over and the slots 7 are formed therein by means of a circular saw or cutter 13. The saw 13 cuts just to the ends of the slots 8 and the small fins 1 1 are then removed by a suitable hand tool so that the ends of slots 7 are in substantial alinement with the ends of slots 8, as shown in Fig. 6.

The completed plate then appears as shown in Figs. 2 and 7 and is adapted to be used as shown in Fig. 1 for the screening of pulp. It is obvious that as the pulp fibres pass through the slots 7 there are no projecting edges to catch the fibres and allow them-to collect and hang down from the plate. My improved plate difl'ers very ma- .terially in this respect from the plates heretofore constructed, and in order to make clear the advantages of my improved plate and method of manufacture over what has been done before, the method of making one of these prior plates is illustrated in Figs. 3 and 4 inclusive.

Referring to Fig. 3, slots 15 are first formed in a plate 16 by means of a cutter 17 of substantially the same form as the cutter 10. The next step in the formation of the plate consists in cutting the slots 18 by means of a'saw 19, the diameter of which is great enough to allow the slots 18 to be cut a short distance into the shoulders 20 at the endsof the slot 15, as indicated at 21.

The completed plate then appears as shown in Figs. 2 and 7 from which it is apparent that the slots 18 are considerably shorter than the greatest dimensions of the slots 15, owing to the existence of the shoulders 20 at the ends of the slots 15. It has been found that when plates constructed as shown in Fig. 7 are used in connection with the diaphragm 3 of Fig. 1, the pulp fibres in passing through the slots 18 will collect in the spaces 21 at the ends of the slots 18 and will tend to form strings or hairs 21 hangin from the plate 16. It is obvious that the strings will grow in size as the pulp continues to pass through the plate and that finally the strings will break off, due to their own weight, and fall into the pulp on the diaphragm. When pulp containing such strings or hairs of fibre passes into paper, the paper has defects or weak spots caused by the hairs being pressed out and it has been found that when paper containing such defects passes through the paper machine it is liable to break, thereby making it necessary to shut down the machine.

tendency to form strings or hairs. This 05 is due to the fact that the ends of the slots 7 are continuous with the ends of the slots 8 and consequently there are no projections to catch the fibres as they pass through the slots 7. Furthermore, it is apparent that my improved plate has a much greater pulp screening capacity than plates heretofore constructed of the same overall dimensions, owing to the fact that the slots 7 extend the full length of the slots 8, whereas in the plate shown in Fig. 1, the total length of the slots 15 at the bottom of the plate is considerably greater than the total length of the slots 18 at the top of the plate. Inasmuch as an ordinary paper mill employs many hundreds of square feet of screen plates, and it is customary to form the. plates of relatively expensive metal, such as bronze or brass, it will be readily understood that the substitution in a single paper mill, of my improved plates for plates heretofore constructed, will result not only in increased capacity for the mill, but will also result in a considerable saving in plate material when replacing worn out plates.

Furthermore, the complete elimination of hairs in the screened pulp greatly reduces breaks during the process of paper manufacture and therefore results in a great saving of both time and labor which is ordinarily lost in starting the entire process again following a break due primarily to the use of plates which permit the formation of hairs. Lastly, the use of my improved plates permits washing to be carried on much more effectively] than with the old style plates, for it is obvious that a stream of water )layed on the top of-one of my improved p ates will completely clean both sets of slots of any fibres which may remain therein, whereas with the old style plates it would be almost impossible to clean the ends of the slots 15 owing to the existence of the shoulders 20.

While I have shown my method of manufacture as being carried out by specific forms of tools, it is obvious that certain modifications in the tools can be made without departing from the spirit and scope of my invention, and I desire therefore, that only such limitations be imposed thereon as may come within the scope of the appended claims.

I claim,

1. A screen plate for paper manufacture consisting of a plate provided with communicating slots of different widths on opposite faces thereof, the said slots being of substantially the same overall length with their end walls substantially in alinement.

2. A screen plate for paper manufacture consisting of a plate provided with communicating slots of different widths on opposite faces thereof, the end walls of said slots being substantially in alinement.

3. A screen plate for paper manufacture consisting of a plate provided With communicating slots of different Widths on opposite faces thereof, the ends of said slots being substantially in alinement to provide unbroken surfaces extending from one face of said plate to the other.

4. A screen plate for paper mills consisting of a plate provided on opposite faces thereofWith communicating slots of different Width having a common center line, the end Walls of said slots being substantially in alinement to provide substantially unbroken surfaces extending from one face of said plate to the other.

5. A screen plate for paper manufacture, consisting of a plate provided with com- Inunicating slots of difierent Widths on opposite sides thereof, the said slots being of substantially the same overall length, with the narrowslots open for their entire length 15 to the full Width of the Wide slots.

Dated this third day of September, 1921.

WALTER S. HALL. 

